UA could've sold more than it did. She stopped promoting it by Spring 2013, and when she finally released the PIU/WN videos, the era was already long done. She was busy touring while she wasn't promoting though, and the tour was a huge success.
At least in the US, UA is a ridiculously high price on iTunes - it's $15.99 for 15 songs.
TTT/UA's longevity & final sales aren't totally ideal, but they kept her one of the top girls in pop music post-Loud (which was HUGE). It's fair to say neither album underperformed. She got some of the biggest hits of her career from the singles of these albums with WFL, Diamonds & Stay. I would say Stay has left a bigger impression on the GP than Diamonds for sure.
move on
It's funny though that she got him get rid of his guns. The only reason she's alive is cuz her mom used a gun to kill her abusive father. A gun is the reason Charlize Theron is alive.